I would expect that you would be able to export the Apple root certificate as well and import it into Windows. Shame on Apple and on Microsoft if they're forcing us to buy two separate code signing certificates to support both platforms.

According to the document, you can sign a Mac app with a third-party certificate using the codesign command, so it looks like you don't need an Apple developer certificate specifically unless you want to sell in their App store, in which case you can get one simply by paying the required $100 annual fee.

I have not yet been able to find any specific information on the root certificate problem when importing an Apple developer certificate into Windows for signing Windows apps.

To follow up further, I exported the Apple Root CA and Apple Root Certificate Authority system root certs as p7b files and installed them into the Trusted Root Certification Authorities store in Windows 8. I got a warning message in Windows that Apple was unrecognised as a trusted certificate authority so I should be wary of installing the root certificates because any certificates signed by Apple would be accepted as valid.

I then exported the Apple Code Signing Certificate Authority system cert as a p7b file and installed it in Windows 8 and it showed as valid in the Windows cert manager. I don't know if this will work for the Apple developer code signing certificate because I don't have one, but it looks promising based on this experiment.

The same is what i tested but clients can't verify cause they need a root cert too.

That's unfortunate. That means you must have an expensive third-party cert to sign Windows apps and an Apple developer cert if you want to sell in their App store. It's a rather messed up state of affairs not to have a standard cert that will work cross platform.

According to the document, you can sign a Mac app with a third-party certificate using the codesign command, so it looks like you don't need an Apple developer certificate specifically unless you want to sell in their App store, in which case you can get one simply by paying the required $100 annual fee.

I have not yet been able to find any specific information on the root certificate problem when importing an Apple developer certificate into Windows for signing Windows apps.

That's what the docs says, but if you _dont_ use an 'Apple Developer ID' certificate, Mac OS X 10.7.5 & OS X 10.8 by default will not allow your app to open. When you signup with Apple, they give you two certs, one for the App Store and a 'Developer ID' cert.

The Gatekeeper security settings in Mountain Lion give you the option of installing both App Store apps and third-party apps signed with recognized code signing certificates. I have tested it using a Comodo certificate and it's not a problem. However, you do need an Apple Developer certificate if you want to sell in the App Store.